1. Technical Field
Embodiments of the invention relate to determining engine fuel limits, such as those in marine propulsion systems.
2. Discussion of Art
Marine propulsion systems typically include a diesel engine and a fixed or controllable pitch propeller. In the United States, marine diesel engines must meet U.S. EPA (Environmental Protection Agency) emissions regulations since they emit, among other things, nitrogen oxide and particulate matter. Emissions testing for EPA compliance utilizes a marine engine's maximum rated power. In particular, maximum engine power curves are used in determining duty cycles for test purposes.
Known methods of creating marine engine power curves use static fuel limit tables. These tables, which typically reside in an engine's ECU (engine control unit), limit the amount of fuel that can be injected into an engine and thereby limiting its power. Fuel limit tables are created based on performance data taken from an exemplary test engine and do not take into consideration engine to engine variation in fueling amounts. As a result, different production engines of the same type or model can have varying maximum powers. This varying engine power requires revisions to engine control unit software to create new fuel limit tables for underperforming engines. Moreover, EPA emissions regulations only allow for a relatively small degree of variation in maximum engine power for emissions testing.
Furthermore, known methods of creating engine power curves do not allow users to vary the curve based on vessel requirements. Similarly, known methods do not account for the application type for which the engine will be used.
As will be appreciated, it is desirable to create engine fuel limits that take into consideration engine to engine fueling variances and to be able to easily modify or customize the same. It is also desirable that all engines of a specific type or model produce the same power at any given speed.